The objective of this research is to study the neurophysiology and neuroanatomy of non-fornical hippocampal efferent pathways. Projections from the hippocampus and subiculum to the entorhinal cortex will be studied, as well as projections from the entorhinal cortex to the amygdala. Physiologically characterized neurons in the rat will be marked with intracellular injections of horseradish peroxidase (HRP); the morphology and axonal projections of the marked neurons will be correlated with the neurophysiologic data in order to provide information about the synaptic organization of the pathways. Retrograde HRP transport studies will be performed in squirrel monkeys in order to provide further information about these pathways in a primate species. Further knowledge about these pathways has potential health-relevance, since the hippocampal formation is exceedingly seizure-prone, and appears to be an important substrate for learning, memory, and emotionality. This efferent system could thus be an important route for seizure propagation in temporal lobe epilepsy, and could also be involved in emotional disorders.